System - a group of physiologically or anatomically connected organs or areas; "the body features a system of organs for digestion" An oxygen atom has 6 electrons in its outer (valence) shell, which could maintain a total of 8 electrons. When an oxygen atom kinds just one chemical bond, it https://becketttaejo.hazeronwiki.com/7011836/helping_the_others_realize_the_advantages_of_elfa